Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 112351 AFDBTV AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BURLINGTON VT 651 PM EST THU FEB 11 2016 .SYNOPSIS... A WEAK UPPER LEVEL TROUGH ACROSS THE ST. LAWRENCE VALLEY WILL TRACK EASTWARD WITH JUST A FEW FLURRIES OR SNOW SHOWERS THROUGH THE FIRST HALF OF TONIGHT. AS THIS FEATURE MOVES EAST...SKIES WILL BECOMING PARTLY TO MOSTLY CLEAR AFTER MIDNIGHT WITH SURFACE HIGH PRESSURE BUILDING IN FROM THE WEST. IT WILL BE COLD WITH OVERNIGHT LOWS GENERALLY ZERO TO 5 ABOVE IN THE CHAMPLAIN AND CONNECTICUT VALLEYS...AND GENERALLY ZERO TO 10 BELOW ELSEWHERE. ANOTHER UPPER LEVEL LOW AND ARCTIC FRONTAL ZONE WILL APPROACH FROM THE GREAT LAKES AND SOUTHEASTERN ONTARIO LATE IN THE DAY FRIDAY INTO FRIDAY NIGHT. THIS FEATURE WILL BRING LOCALIZED LAKE EFFECT SNOWS TO SOUTHERN ST. LAWRENCE COUNTY...AND THEN THE POTENTIAL FOR SNOW SHOWERS OR SQUALLS ALONG THE ARCTIC FRONT AS IT MOVES THROUGH DURING FRIDAY NIGHT. THIS WILL USHER IN THE COLDEST AIR MASS OF THE WINTER FOR THE WEEKEND...WITH BITTERLY COLD TEMPERATURES. A MODERATION IN TEMPERATURES WILL BEGIN MONDAY...WITH A STORM SYSTEM BRINGING MIXED WINTRY PRECIPITATION POTENTIALLY FOR TUESDAY. && .NEAR TERM /THROUGH FRIDAY NIGHT/... AS OF 631 PM EST THURSDAY...FORECAST REMAINS IN GOOD SHAPE FOR TONIGHT. DID INCREASE POPS AND SKY COVER SLIGHTLY TO ACCT FOR CURRENT FLURRY/SHSN ACTIVITY, SOME OF WHICH MAY BE A RESULT OF THE WARM LAKE CHAMPLAIN WATERS WHERE LAKE INDUCED CAPE IS AVERAGING AROUND 700 J/KG. SOME MINOR ACCUMULATIONS OF A DUSTING TO ABOUT AN INCH ARE POSSIBLE THIS EVENING, ESPECIALLY IN THE HIGHER ELEVATIONS. FROUDE DATA INDICATING BLOCKED FLOW DEVELOPING OVERNIGHT WHICH WILL ACT TO SLOW CLEARING PROCESS SOMEWHAT DESPITE WEAK BUBBLE HIGH MOVING IN FROM THE WEST. LOW TEMPERATURES GENERALLY APPEAR ON TRACK THOUGH DID LOWER HOURLY READINGS A BIT AS VALUES HAVE FALLEN A BIT QUICKER THAN EARLIER INDICATIONS. HAVE A GREAT EVENING. PRIOR DISCUSSION... COMPACT MID-LEVEL VORT EVIDENT IN IR AND VIS IMAGERY ACROSS THE ST. LAWRENCE VALLEY WILL SHIFT EWD ALONG THE INTL BORDER AND SHIFT EAST OF VT BY 06Z. LOOKING AT JUST A FEW LIGHT SNOW SHOWERS WITH THIS FEATURE THROUGH THIS EVENING...AIDED BY STEEP LOW-LEVEL LAPSE RATES (IN LOW-LEVEL CAA REGIME) AND WLY 850MB FLOW OF 15-20KTS PROVIDING SOME UPSLOPE INTO THE ADIRONDACKS AND NRN GREENS. ANY ACCUMULATION EXPECTED TO BE AN INCH OR LESS...MAINLY CONFINED TO AREAS OF OROGRAPHIC ASCENT. OTHERWISE...IT WILL BE A COLD NIGHT WITH CLEARING SKIES AS NARROW SFC RIDGE BUILDS IN BRIEFLY FROM THE WEST AFTER 06Z...CRESTING ACROSS VT AROUND 12Z FRIDAY. CORE OF COLDEST 850MB TEMPS WILL BE IN PLACE THIS EVENING...GENERALLY -24C TO -26C. SOME RADIATIONAL COOLING AND THIN LAYER OF SNOW COVER WILL AID IN RADIATIVE COOLING...ESPECIALLY LATE WITH CLEARING AND DIMINISHING WIND. LOOKING AT OVERNIGHT LOWS ZERO TO 5 ABOVE FOR THE CHAMPLAIN VALLEY AND AROUND SPRINGFIELD VT...AND GENERALLY ZERO TO -10F ELSEWHERE. FRIDAY INTO FRIDAY NIGHT: SECONDARY ARCTIC BOUNDARY AND ASSOCIATED UPPER VORT DIGS ESEWD ACROSS THE NORTHERN GREAT LAKES. THIS ALLOWS SFC-850MB FLOW TO BACK AHEAD OF THE TROUGH AXIS. LOW-LEVEL TRAJECTORIES FROM LAKE ONTARIO BRING LAKE EFFECT SNOW BANDS INTO ST. LAWRENCE COUNTY...LIKELY STARTING AROUND 14-15Z FRIDAY PER BTV LOCAL WRF RUNS. PERIODS OF LAKE EFFECT SNOW WILL GENERALLY BE CONFINED TO ST. LAWRENCE AND FRANKLIN COUNTIES DURING THE DAYLIGHT HRS FRIDAY...WITH MAINLY DRY CONDITIONS ELSEWHERE WITH VARIABLY CLOUDY CONDITIONS AND WEAK S-SW FLOW. LAKE EFFECT SNOW WILL BE BRIEFLY AUGMENTED BY LOW-LEVEL FRONTOGENETIC FORCING AND CONVERGENCE AS ARCTIC BNDRY SWEEPS INTO NRN NY BETWEEN 02-05Z...AND ACROSS VT AFTER MIDNIGHT. SHOULD SEE POTENTIAL SNOW SQUALLS ALONG THE BNDRY AS IT MOVES ACROSS ENTIRE CWA DURING THE OVERNIGHT HRS FRIDAY NIGHT. WILL SEE LAKE EFFECT SNOW END BEHIND ARCTIC BNDRY AS MEAN FLOW VEERS RAPIDLY FROM SW-NW. WILL BE REPLACING THE LAKE EFFECT SNOW WATCH WITH A LAKE EFFECT SNOW ADVISORY THIS AFTN FOR SRN ST. LAWRENCE COUNTY 14Z FRIDAY THROUGH 06Z SATURDAY TO COVER LAKE EFFECT SNOW AMOUNTS GENERALLY 3-6". WILL PROBABLY SEE A COUPLE OF COMMUNITIES IN EXCESS OF 6" SNOWFALL AROUND FINE, NY...BUT ANTICIPATE THAT WILL BE ISOLD GIVEN TRANSITIONAL NATURE OF THE LAKE EFFECT SNOW BAND AS LOW-LEVEL FLOW BACKS AND THEN QUICKLY VEERS WITH FROPA. OTHERWISE...WILL SEE A DUSTING TO 2" FRIDAY NIGHT WITH ARCTIC FRONTAL PASSAGE WITH SNOW SHOWERS AND POSSIBLE SQUALL ACTIVITY. SNOW RATIOS GENERALLY 20:1 TO 25:1 GIVEN VERY COLD AIR MASS...AND NOT EXPECTING ANY SIGNIFICANT IMPACTS (ALSO CONSIDERING PRE-DAWN HRS SATURDAY MORNING WITH LIGHT TRAFFIC). HIGH TEMPERATURES ON FRIDAY GENERALLY GENERALLY TEENS TO LOWER 20S. STRONG CAA LATE FRIDAY NIGHT WILL BRING TEMPS DOWN TO 5 TO 10 BELOW ACROSS THE ADIRONDACKS AND ST. LAWRENCE VALLEY BY DAYBREAK SATURDAY...INCLUDING WIND CHILLS 25 TO 30 BELOW (SEE FORTHCOMING SHORT-TERM FORECAST SECTION FOR MORE DETAILS ON DANGEROUSLY LOW WIND CHILLS FOR THE WEEKEND). LOWS ACROSS VERMONT AND THE NY SIDE OF THE CHAMPLAIN VALLEY FRIDAY NIGHT MAINLY ZERO TO +7F. && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 347 PM EST THURSDAY...WIND CHILL WATCH IN EFFECT EARLY SATURDAY MORNING THROUGH SUNDAY. COLD ARCTIC AIR WILL CONTINUE TO FILTER INTO THE NORTH COUNTRY IN THE WAKE OF STRONG COLD FRONT SATURDAY. TEMPERATURES WILL FALL THROUGHOUT THE DAY...WITH MAXES OCCURRING IN THE MORNING IN THE NEGATIVE SINGLE DIGITS ACROSS MOST OF NORTHERN NY...AND THE POSITIVE SINGLE DIGITS ACROSS THE CHAMPLAIN VALLEY EASTWARD. MOUNTAIN TOPS WILL REMAIN BELOW ZERO. PRESSURE GRADIENT INCREASES AS DEPARTING SURFACE LOW MOVES NEWD AND RIDGING BUILDS OVER THE MID-WEST. THIS WILL RESULT IN BREEZY CONDITIONS AT THE SURFACE WITH GUSTS 15-25KTS POSSIBLE. COLD TEMPERATURES COMBINED WITH WINDS WILL RESULT IN WIND CHILLS OF 20 TO 40 DEGREES BELOW ZERO THROUGHOUT THE WEEKEND AS 850MB TEMPERATURES FALL INTO -30C TO -25C EARLY SUNDAY. THIS COLD FRIGID AIR IS EXPECTED TO PERSIST UNTIL SUNDAY NIGHT WHEN THE RIDGE OF HIGH PRESSURE MOVES OVERHEAD AND WINDS SUBSIDE WHILE TEMPERATURES BEGIN TO INCREASE ALOFT. AIR TEMPERATURES SATURDAY NIGHT WILL BE BELOW ZERO...RANGING FROM NEGATIVE TEENS TO NEGATIVE 20S. SUNDAY WILL SEE MAX TEMPERATURES IN THE SINGLE DIGITS ABOVE AND BELOW ZERO. PRECIPITATION-WISE...SOME RESIDUAL MOISTURE IN THE NORTHWESTERLY WINDS WITH FROUDE NUMBERS SHOWING SLOW MOVING/BLOCKED UPSLOPE FLOW WILL KEEP SNOW SHOWERS ACROSS THE NORTHEAST KINGDOM AND WESTERN SLOPES OF THE GREENS AND NORTHERN ADIRONDACKS FOR SATURDAY WITH A DRYING TREND THEREAFTER. WITH LAKE CHAMPLAIN WATER TEMPERATURES STILL IN THE MID 30S, CANNOT RULE OUT SOME STEAM CLOUDS DEVELOPING IN COLDER AIR AND POSSIBLE TEA KETTLE TYPE SNOW SHOWERS IN THE CHAMPLAIN VALLEY SATURDAY AND SUNDAY. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 347 PM EST THURSDAY...SURFACE HIGH PRESSURE WILL SLOWLY SHIFT EASTWARD SUNDAY NIGHT INTO MONDAY WITH SLIGHT RIDGING ALOFT. ON THE WESTERN SIDE OF THE RIDGE AXIS, SOUTHERLY FLOW WILL HELP MODERATE TEMPERATURES MONDAY...WITH MAXES REACHING THE 20S. THE NEXT SIGNIFICANT SYSTEM WILL EVOLVE FROM DIGGING 500MB TROUGH THAT APPROACHES FROM THE WEST MONDAY NIGHT INTO TUESDAY. WHILE MODELS STILL DIFFER ON TRACK OF ASSOCIATED SURFACE THAT DEVELOPS, EXPECT LOW TO BEGIN BRINGING PRECIPITATION IN FROM THE SOUTH ON TUESDAY. BOTH GFS AND ECMWF CURRENTLY BRING SIGNIFICANT WARMING TO THE NORTH COUNTRY AND RESULT IN ABOVE FREEZING TEMPERATURES ON TUESDAY. TEMPERATURES MAY BE WARM ENOUGH FOR PRECIP TO TRANSITION TO RAIN LATE TUESDAY. BUT AS THE LOW LIFTS NORTH AND EAST, COLD AIR RETURNS TO THE REGION ON THE BACKSIDE OF THE SYSTEM WITH SNOW SHOWERS EXPECTED. MULTIPLE VORTICES IN 500MB TROUGH MAY KEEP CHANCE FOR PRECIPITATION INTO WEDNESDAY AS THE MAIN SURFACE LOW CONTINUES TRACKING NORTHWARD INTO COASTAL CANADA. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... THROUGH 00Z SATURDAY...TREND TOWARD VFR OVERNIGHT AS UPPER LEVEL RIDGE MOVES OVER THE AREA AND NW FLOW RELAXES GENERALLY AFTER 06Z. AT BTV...NW FLOW ACROSS THE 37 DEGREE WATERS OF LAKE CHAMPLAIN MAY BRING FLURRIES OR EVEN A SNOW SHOWER FOR A WHILE TONIGHT. FOR NOW JUST MENTIONING AS VCTY SNOW SHOWERS BUT ITS ENTIRELY POSSIBLETHAT CIGS GO MVFR AND VSBY IFR FOR A BRIEF PERIOD BEFORE 04Z. NOT EXPECTING MUCH ACCUMULATION ON RUNWAYS. OTHERWISE MVFR CIGS (2-3 KFT) GENERALLY LIMITED TO SLK OTHERWISE THE TREND TO VFR LATE TONIGHT INTO FRIDAY MORNING. WILL BEGIN TO SEE MVFR CEILINGS AND LOCALLY IFR VSBY AT SLK/MSS WITH -SHSN POSSIBLE AFTER 17Z ASSOCIATED WITH INCREASING SWLY FLOW FROM LAKE ONTARIO AND FRINGE IMPACT FROM LAKE EFFECT SNOW BANDS. NW WINDS BRIEFLY GUSTY 15 TO 20KTS THRU EARLY EVENING...THEN GENERALLY LESS THAN 10KTS TONIGHT AND FRIDAY MORNING THEN SHIFTING TO THE S AND SW AROUND 10KTS THROUGH FRIDAY MORNING. S WINDS MAYBE A PROBLEM AT KBTV GROUND OPERATIONS FRIDAY AFTERNOON INTO THE NIGHT WITH DRIFTING OR BLOWING SNOW BY 00Z SAT AND MAY BE GUSTING OVER 30KTS UNTIL THE ARCTIC FRONT PASSES EARLY SAT A.M. OUTLOOK 00Z SATURDAY THROUGH MONDAY...LCL VLIFR IN SNOW SQUALLS BRIEFLY POSSIBLE FRIDAY NIGHT 02-05Z ACROSS NRN NY AND 05-09Z ACROSS VT AS ARCTIC FRONT MOVES THRU...WITH VSBY BRIEFLY LESS THAN 1/2 MILE AND A WIND SHIFT TO NW WITH GUSTS 20 TO 30 KTS. MODEST IMPACT TO AIRPORT GROUND OPERATIONS WITH DUSTING TO 2" SNOWFALL PSBL. GENERALLY VFR AFTER 12Z SATURDAY WITH FLURRIES POSSIBLE. NW WIND GUSTS TO 25KT POSSIBLE SATURDAY AFTN AND EVE. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...WIND CHILL WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY EVENING FOR VTZ001>012-016>019. NY...WIND CHILL WATCH FROM LATE FRIDAY NIGHT THROUGH SUNDAY EVENING FOR NYZ026>031-034-035-087. LAKE EFFECT SNOW ADVISORY FROM 9 AM FRIDAY TO 1 AM EST SATURDAY FOR NYZ029-087. && $$ SYNOPSIS...BANACOS/JMG NEAR TERM...BANACOS SHORT TERM...KGM LONG TERM...KGM AVIATION...BANACOS/SISSON

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